In Policy and Charging Control (PCC), e.g. as described in 3GPP technical specification (TS) 23.203 (3GPP: 3rd Generation Partnership Project), the Application Function (AF) is an element offering applications that require dynamic policy and/or charging control of traffic plane resources. Policy control may comprise for example functionalities for:                Binding, e.g. the generation of an association between a service data flow and the Internet Protocol Connectivity Access Network (IP CAN) bearer transporting that service data flow;        Gating control, e.g. the blocking or allowing of packets, belonging to a service data flow, to pass through to a desired endpoint;        Event reporting, e.g. the notification of and reaction to application events to trigger new behavior in the user plane or the reporting of events related to the resources in a gateway (GW), e.g. a Policy and Charging Enforcement Function (PCEF);        Quality of Service (QoS) control, e.g. the authorization and enforcement of the maximum QoS that is authorized for a service data flow or an IP CAN bearer, or        bearer establishment, e.g. for IP CANs that support network initiated procedures for IP CAN bearer establishment.        
In general terms, a bearer is an information transmission path with defined parameters, e.g. capacity, delay and bit error rate, etc. An IP CAN bearer can thus be described as an IP transmission path of defined capacity, delay and bit error rate, etc. and an IP CAN session as the association between a user equipment (UE) represented by an Internet Protocol (IP) address or UE identity information and a packet data network (PDN) represented by a PDN ID, e.g. an Access Point Name (APN). An IP CAN session incorporates one or more IP CAN bearers. A service data flow is an aggregate set of packet flows that matches a service data flow template, i.e. the set of service data flow filters in a PCC rule, required for defining a service data flow.
In the case of the IP Multimedia Subsystem (IMS) in the core network, a function termed as Proxy-Call Session Control Function (P-CSCF) plays the role of AF at the Session Initiation Protocol (SIP) signaling plane. The PCEF is the entity that can provide service data flow detection, charging and policy enforcement over the user plane traffic. Within a General Packet Radio Service (GPRS) access network, the PCEF is located in a node termed as Gateway GPRS Support Node (GGSN) while within the Evolved Packet System (EPS) architecture the PCEF is located in the PDN GW. A policy controller termed as Policy and Charging Rules Function (PCRF) is placed between the application layer (e.g. IMS) where service session characteristics are negotiated and the media plane where the actual service is being delivered.
FIG. 1 shows a simplified illustration of a PCC architecture. In the architecture of FIG. 1, the PCRF installs PCC rules at the PCEF that, when the bearer binding is allocated at the PCEF, associates the PCC Rules with the IP-CAN bearer that carries the service data flows. For GPRS and EPS access this triggers the PCEF to send traffic flow template (TFT) filters to the UE, which specifies the contents of the service data flows.
In precondition signaling, e.g. for IMS (as described e.g. in 3GPP TS 23.228 and TS 24.229), the UE sets the precondition attributes for Session Description Protocol (SDP) media and sets parameters to “mandatory” for media which require local resources when resources for the media are not available yet. A precondition is a set of constraints about the session, which are introduced during the session initiation. The recipient of the session generates an answer, but does not alert the user or otherwise proceed with session establishment until the preconditions are met. This can be known through a local event, e.g. a confirmation of a resource reservation, or through a new set of constraints sent by the caller.
The P-CSCF (or AF) interrogates with the PCRF to request the AF session to be authorized. The PCRF authorizes the AF session and pushes down PCC rules to the PCEF for the SDP media which require additional resources.
The PCEF enforces the policies and initiates resource reservation for media which require additional resources by IP CAN specific procedures.
For GPRS, the GGSN initiates appropriate Packet Data Protocol (PDP) context and EPS bearer procedures. For EPS, this is accomplished by the PDN GW.
The PDP context and EPS bearer procedures include packet filters corresponding to the SDP media allowing the UE to bind the resource reservation with the SDP media so the UE can then initiate an SDP update indicating that resources are now available for the SDP media which didn't have resources available before. If the UE would not get any packet filter update, then the UE would not know whether the network has allocated resources for the SDP media. For example, if there was a PDP context or EPS bearer activation or modification the UE would not know whether it was for the SDP media or for any other application running in the UE.
The set-up of a “QoS-Assured” session will not complete until required resources have been allocated to the session. In a QoS-Assured session, the QoS bearer for the media stream shall be successfully established according to the QoS preconditions defined at the session level before the UE may indicate a successful response to complete the session and alert the other end point. The principles for when a UE shall regard QoS preconditions to be met are:                A minimum requirement to meet the QoS preconditions defined for a media stream in a certain direction, is that an appropriate IP CAN bearer is established at the local access for that direction.        Segmented resource reservation is performed since the end points are responsible to make access network resource reservations via local mechanisms.        The end points shall offer the resources they may want to support for the session and negotiate to an agreed set. Multiple negotiation steps may be needed in order to agree on a set of media for the session. The final agreed set is then updated between the end points.        The action to take in case a UE fails to fulfil the preconditions, e.g. failure in establishment of a Resource Reservation Protocol (RSVP) session, depends on the reason for failure. If the reason is lack of resources in the network, e.g. an admission control function in the network rejects the request for resources, the UE shall fail to complete the session. For other reasons, e.g. a lack of an RSVP host or proxy along the path, the action to take is a local decision within the UE. For example, the UE may choose to fail to complete the session or attempt to complete the session by no longer requiring some of the additional actions.        
However, according to 3GPP TS 24.008 and 24.301 the number of packet filters that can be installed in a TFT of the UE is limited. More specifically, the amount of precedence values is limited for a PDN connection i.e. all bearers connected to the same default bearer. The precedence values specify the order in which packet filters are applied when forwarding data packets to bearers and can, therefore, not have the same value for different packet filters. According to 3GPP TS 24.008 the same precedence value for different filters will result in a syntactical error. If a large number of packet filters is installed it may increase the need to reassign new precedence values to the installed packet filters if a packet filter to be installed should receive a precedence value that is already taken by another packet filter, and there may be a need to increase the amount of possible precedence values. Accordingly, if the PCEF always forwards all packet filters of the PCC rules to the UE there might be a need to extend the allowed packet filters in a TFT. This would in turn require larger information elements and thus increase the signaling overhead. Further, forwarding all packet filters of the PCC rules to the UE, generates a high signaling load.
Accordingly, there is a need for techniques which allow for efficiently controlling installation of packet filters in the UE.